The present invention relates to apparatus and method for transmitting data and, more particularly, to apparatus and method for transmitting variable-bit rate data on a digital serial bus having a predetermined transmission rate. The invention also relates to apparatus and method for transmitting variable-bit rate data on a digital serial bus with means for pre-detecting the bit rate of intervals of the variable-bit rate to be transmitted.
As is known, various types of digital video-audio equipment, for example, DVD reproducing devices, digital VTRs, digital televisions, etc., are currently available for consumer use. Several such devices reproduce or receive digital video/audio signals, convert those signals into analog signals, and supply the analog signals to analog-type video/audio equipment. It is also generally desirable to supply from such equipment digital video/audio signals to, for example, a personal computer, a digital television receiver, or other type of digital device.
The communication system IEEE-1394 is a digital serial bus which has been proposed as a means for transmitting such digital video/audio signals between digital devices. Referring to FIG. 1 of the drawings, an exemplary block diagram of an IEEE-1394 system that includes an IEEE-1394 bus 901 and various digital devices 902-907 is shown. In the exemplary block diagram, the IEEE-1394 bus is coupled between a DVD reproducing apparatus 902, a digital VCR 903, a digital broadcasting receiver 904, a digital television receiver 905, a digital television receiver 906 and a personal computer 907. As shown, digital video/audio data is supplied from DVD reproducing apparatus 902 via the IEEE-1394 bus to digital television receiver 906, and digital video/audio data supplied from digital broadcasting 904 is supplied via bus 901 to digital television receiver 905. Given an IEEE-1394 bus with a transmission rate of, for example, 100 Mbps, and video/audio data is organized into xe2x80x9cunitsxe2x80x9d of data, then in accordance with IEEE-1394 standard, 4915 units of data can be transmitted during each 125 xcexcsec transmission cycle of the bus. In accordance with this standard, the number of units transmitted corresponds to the bit rate of the signal to be transmitted. For example, to realize a communication speed of approximately 10 Mbps, which corresponds to the mean bit rate of a typical video signal, then approximately 1200 units are needed. However, to realize a communication speed of approximately 2 Mbps, which is the mean bit rate of an audio signal, then approximately 704 units are needed.
One limitation of the above discussed IEEE-1394 standard is that signals are transmitted only after their transmission rate (i.e., bit rate) is determined. However, DVD reproducing devices that employ MPEG encoders/decoders reproduce digital video/audio data at a variable rate and, thus, an IEEE 1394-bus previously has been unable to transmit variable rate data reproduced from such devices.
Therefore, it is an object of the present invention to provide an apparatus and method for transmitting digital video/audio data which overcome the shortcomings of the above described system.
Another object of the present invention is to provide apparatus and method which is operable to transmit variable rate digital video/audio data in accordance with the IEEE-1394 standard.
Various other objects, advantages and features of the present invention will become readily apparent to those of ordinary skill in the art, and the novel features will be particularly pointed out in the appended claims.
In accordance with one embodiment of the present invention, apparatus and method are provided for detecting a data rate of variable rate data at predetermined intervals of time, establishing a rate of transmission of the variable rate data in accordance with the detected data rate, and transmitting in accordance with the established transmission rate the variable rate data on a transmission line that requires the transmission rate to be predetermined.
As one aspect of the present invention, a bandwidth of the transmission line that is required to transmit the variable rate data having the detected data rate is secured.
As a feature of this aspect, given a transmission line with a plurality of transmission cycles, the data rate of the variable rate data to be transmitted during each of the cycles is detected.
As another feature of this aspect, a new bandwidth is secured for each cycle of the transmission line in accordance with the detected data rate of the variable rate data to be transmitted during the respective cycle.
In accordance with another embodiment of the present invention, apparatus and method are provided for controlling the reproducing of a signal from a record medium in accordance with a control signal to produce a variable rate signal, processing the produced variable rate signal (e.g., by an MPEG decoder), generating the control signal in accordance with a condition of processing of the produced variable rate signal, and transmitting the variable rate signal on the transmission line.
As one aspect of this embodiment, the transmitted variable rate signal is received and processed in a similar manner as that of the produced variable rate signal (e.g., by a second MPEG decoder), but such second processing does not generate a control signal (similar to the earlier generated control signal) that represents a condition of the second processing.
In accordance with a further embodiment of the present invention, apparatus and method are provided for controlling the reproducing of a signal from a record medium in accordance with a control signal to produce a variable rate signal, transmitting from a transmission side the variable rate signal on the transmission line, receiving the variable rate signal transmitted on the transmission line, processing the received transmitted variable rate signal, generating the control signal in accordance with a condition of processing of the received transmitted variable rate signal, transmitting the generated control signal on the transmission line, and receiving at the transmission side the transmitted control signal, wherein the received transmitted control signal is utilized to control the reproducing of a signal from the record medium.